Which of the following domains include organisms that have a nucleus and other membrane-bound organelles?
A. Archaea only B. Eukarya only C. Archaea and Eukarya D. Bacteria only
The Correct Answer and Explanation is :
The correct answer is B. Eukarya only.
Explanation:
The classification of living organisms is based on a hierarchical system that includes three main domains: Archaea, Bacteria, and Eukarya. Understanding the cellular structure of these domains is crucial to distinguishing them.
- Eukarya: This domain includes organisms whose cells possess a nucleus and other membrane-bound organelles, such as mitochondria and endoplasmic reticulum. Eukaryotic organisms can be unicellular (like protists and yeast) or multicellular (such as plants, animals, and fungi). The presence of a true nucleus allows for more complex regulation of gene expression and a higher level of organization compared to prokaryotic cells. The compartmentalization provided by membrane-bound organelles enables specialized functions within the cell, making eukaryotic organisms more versatile and capable of complex processes.
- Archaea: While archaea are often similar to bacteria in their prokaryotic structure (they lack a nucleus and membrane-bound organelles), they are genetically and biochemically distinct from bacteria. Archaea can thrive in extreme environments, such as hot springs and salt lakes, and some possess unique features like ether-linked lipids in their cell membranes. However, they do not have a nucleus or membrane-bound organelles, which is a defining characteristic of eukaryotes.
- Bacteria: Like archaea, bacteria are prokaryotic organisms that lack a nucleus and membrane-bound organelles. They have a simpler cell structure compared to eukaryotes and typically have a single circular chromosome and a rigid cell wall.
In summary, only the domain Eukarya includes organisms with complex cellular structures characterized by the presence of a nucleus and membrane-bound organelles, setting it apart from the other two domains, which are entirely prokaryotic.